Contraindication for blood thinners common in AFib patients, associated with high stroke risk

Roughly 12 percent of patients with medical claims for atrial fibrillation (AFib) are contraindicated for blood thinning treatment and remain at a high risk for stroke, a new study found.

Through administrative claims for Medicare insurance, researchers identified 1.3 million people with AFib. Among them, 161,606 had at least one documented oral anticoagulant (OAC) contraindication event based on bleeding risk.

Because of this, the researchers wrote, they often don’t receive OAC therapy despite having high CHADS2 and CHADS2-VASc scores—calculations of stroke risk for AFib patients.

“We show that these risk scores are predictive of the stroke risk in this study population and that the risk of thromboembolic events is considerable,” wrote lead author Björn Redfors, MD, PhD, with the Cardiovascular Research Foundation in New York, and colleagues. They published their findings in JACC: Clinical Electrophysiology.

“Bleeding risk was considerably higher in these OAC naïve patients than in the general OAC treated population. These patients are at considerable risk of life-threatening or disabling bleeding even in the absence of OAC and this bleeding risk increases with increasing CHADS2/CHADS2-VASc scores.”

Redfors and colleagues analyzed 43,248 AFib patients who remained off OAC therapy for one year or died in the hospital. Ischemic stroke occurred in 4.1 percent of patients within one year of their most recent contraindication, while hemorrhagic stroke occurred in 3.6 percent. For patients with previous intracranial bleeding, those percentages rose to 12.2 and 20.3, respectively.

“The risk of both bleeding complications and thromboembolic events were particularly high in patients who had previously had a hemorrhagic stroke,” the authors noted. “In contrast to the overall study cohort, these patients’ risk does not appear to be predicted by CHADS2/CHADS2-VASc scores, which further complicates clinical decision making. It is possible that this is a distinct group of AF patients for whom the relationship between the traditional predictors of thromboembolic events and serious bleeding differ from the general [AFib] population.”

Based on this observation, the researchers suggested alternative approaches are needed to treat patients in this subgroup.